gfx: Struct traits for GpuMemoryBufferId and GpuMemoryBufferType.

services/ui/gpu/interfaces/gpu_service_internal.mojom

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 module ui.mojom;
 
 import "gpu/ipc/common/gpu_info.mojom";
+import "ui/gfx/geometry/mojo/geometry.mojom";
+import "ui/gfx/mojo/buffer_types.mojom";
 
 interface GpuServiceInternal {
   Initialize() => (gpu.mojom.GpuInfo gpu_info);
 
   // Tells the GPU service to create a new channel for communication with a
   // client. The GPU service responds with an IPC handle.
   EstablishGpuChannel(int32 client_id,
                       uint64 client_tracing_id,
                       bool is_gpu_host)
       => (handle<message_pipe> channel_handle);
 };